In conventional retransmission systems for remote sensors, storage apparatuses for backup have been disposed in remote sensors or local servers placed in local locations (measurement locations) to be able to obtain missing data at the time of failures such as failure of communication lines. The conventional retransmission systems have adopted methods of transmitting retransmission requests from management servers via communication lines and retransmitting missing data.
In the conventional retransmission systems, however, it has been necessary to allow the storage apparatuses for backup to be nonvolatile in order to allow the operations of the retransmission systems after failures to be durable. Further, it has been also necessary to stabilize the communication operation of transmitting requests for retransmission from management servers and receiving missing data.